This kind of a common injector includes a fixed core that generates electromagnetic attractive force upon energization of a coil, and a movable core that is attracted to the fixed core and is displaced together with a valving element. Through control of an energization time Ti for the coil, a valve-open time of the valving element is controlled to control a fuel injection period, i.e., injection quantity Q of fuel (see Patent Document 1).
The conventional common control is premised on injection (full lift injection) being performed such that valve-closing operation is started after the valving element reaches a full lift position. For this reason, when a minutely small amount of fuel is injected, the energization time is set at the shortest energization time Ti (full lift minimum time) that enables the full lift injection, and pressure (supply fuel pressure) of fuel supplied to the injector is reduced.
However, at the time of the above-described full lift injection, in the case of injection of a minutely small amount of fuel, the supply fuel pressure needs to be decreased. Accordingly, a spray particle diameter of fuel injected through a nozzle hole becomes large due to the reduction of injection pressure. Thus, atomization of the fuel spray cannot be sufficiently promoted to cause deterioration of combustion efficiency.
On the other hand, in Patent Document 2, there is described the control whereby injection (partial injection) is performed such that the valve-closing operation is started before the valving element arrives at the full lift position by making the energization time Ti shorter than the full lift minimum time. Also through this control, a minutely small amount of fuel can be injected.
As the pressure (sack fuel pressure) of fuel in a portion (sack chamber) of a fuel passage in the injector on a downstream side of a seat part of the valving element becomes higher, the spray particle diameter of fuel injected through the nozzle hole becomes smaller so as to increase the combustion energy obtained. Therefore, it is desirable to raise the pressure (supply fuel pressure) of fuel supplied to the injector, in that the spray particle diameter can be made small.
Nevertheless, a degree of reduction of fuel through the seat part is large immediately after the valving element is opened. Consequently, the sack fuel pressure does not immediately rise despite the raise of supply fuel pressure. Hence, if the above-described partial injection is carried out, injection is ended with the sack fuel pressure remaining not sufficiently increased. Thus, fuel having a small spray particle diameter cannot be injected.